1. Field
A draw solute for forward osmosis, a draw solution including the draw solute, a forward osmosis water treatment device using the same, and a forward osmosis method for water treatment using the same are disclosed herein.
2. Description of the Related Art
Osmosis (or forward osmosis) refers to a phenomenon in which water in a portion of lower solute concentration moves to a solution of higher solute concentration. On the other hand, reverse osmosis is a method of artificially adding pressure to move water in the opposite direction.
Desalination through reverse osmosis is a known technique in the field of water treatment. Generally, reverse osmosis desalination involves artificially adding a relatively high pressure to move water in the opposite direction through a membrane, thereby producing fresh water. Since reverse osmosis requires a relatively high pressure, it also has a higher energy consumption. To increase energy efficiency, forward osmosis using the principle of osmotic pressure has been suggested. As a solute for the osmosis draw solution, ammonium bicarbonate, sulfur dioxide, aliphatic alcohols, aluminum sulfate, glucose, fructose, potassium nitrate, and the like have been used. Among them, an ammonium bicarbonate draw solution is most commonly known, which may be decomposed into ammonia and carbon dioxide and separated at a temperature of about 60° C. after forward osmosis. Furthermore, newly suggested draw solution materials include magnetic nanoparticles having a hydrophilic peptide attached thereto (separated by a magnetic field), a polymer electrolyte such as a dendrimer (separated by a UF or NF membrane), and the like.
In the case of ammonium bicarbonate, it should be heated to about 60° C. or more so as to be vaporized, thus requiring higher energy consumption. Also, since complete removal of ammonia is practically difficult, it is less than desirable to use it as drinking water due to the odor of ammonia. In the case of the magnetic nanoparticles, it is relatively difficult to redisperse magnetic particles that are separated and agglomerated by a magnetic field. It is also relatively difficult to completely remove the nanoparticles, and thus the toxicity of the nanoparticles should be considered. In the case of a polymer electrolyte, polymer ion (dendrimer, protein, etc.) technology requires a nanofiltration or ultrafiltration membrane filter due to the RH size of the polymer of several to dozens of tens of nanometers. It is also relatively difficult to redisperse the agglomerated polymer after filtering.